Fix issues with org queries, and class-level queries generally

I found an issue with the query methods on the Org resource where it was trying to call the singleton client, but didn't have access to it. I found a few other issues along the way, notably:

* had to `require` the `Forwardable` lib in client.rb
* `Org.find_active_by_id` was not scoping to active orgs
* `Org.find_all_active_orgs` was not scoping to active orgs
* `Org.find_all_orgs` implementation could produce duplicate results due in part to the above issue, and the use of `Array#+` to produce a result set.